Field of the Disclosure
The present disclosure relates to a polymer including a phthalocyanine structure, a method for producing the polymer, a pigment composition including the polymer, a pigment dispersion including the pigment composition, and a toner including the pigment composition.
Description of the Related Art
High-order functional polymer compounds have been generally produced by using pendant-like polymers. Pendant-like polymers are produced by introducing a low-molecular-weight compound that serves as a pendant group into the backbone of the polymer and have both function of low-molecular-weight compounds and function of polymers. Polymers including coloring matter serving as a pendant group are markedly useful from the viewpoint of engineering because they enable coloring matter having ease of forming and working, which are the advantages of polymers, to be produced.
In particular, various functional polymers including a phthalocyanine structure that serves as a pendant group have been proposed because such polymers allow the spectral characteristics of phthalocyanine to be utilized. For example, Japanese Patent Laid-Open No. 07-324170 proposes utilization of such a functional polymer as an optical recording medium. In addition, Laibing Wang et al, Polym. Chem. 2014,vol. 5,issue 8,pp. 2872-2879,The Royal Society of Chemistry, United Kingdom reports an example case where such a functional polymer is utilized as coloring matter for photodynamic therapy. International Publication No. 2009/157536 proposes an example case where such a functional polymer is utilized as a colorant or a pigment dispersant.
An example case where the pendant-like polymer is utilized as a pigment dispersant is focused. In general, pigment particles having a small diameter are less likely to be dispersed to a sufficient degree in a medium such as an organic solvent, a molten resin, or the like because strong cohesive forces are likely to act between the pigment particles. If the dispersibility of a pigment is low and the particles of the pigment are coagulated, tinting strength may be reduced.
Accordingly, there has been proposed a technique in which a dispersant is used in combination with a pigment for dispersing the pigment in order to enhance the dispersibility of the pigment. In particular, various dispersants have been proposed in order to enhance the dispersibility of pigments in toner particles.
For example, Japanese Patent Laid-Open No. 2012-067285 discloses a technique for dispersing azo pigments, in which a compound including an azo skeleton structure is used in combination with a binder resin and a pigment in order to produce a toner having good color tone.
Japanese Patent Laid-Open No. 03-113462 discloses a technique in which a polymer including a unit that is sodium styrenesulfonate is used as a dispersant in order to enhance the dispersibility of a phthalocyanine pigment in a cyan toner.
Japanese Patent Laid-Open No. 06-148927 discloses a toner that includes a copolymer constituted by a styrene monomer and an acrylic-acid-ester monomer (or, methacrylic-acid-ester monomer) in order to enhance the dispersibility of carbon black in a black toner.
Japanese Patent Laid-Open No. 07-324170 and International Publication No. 2009/157536 describe a method in which a polymerizable monomer including a phthalocyanine structure is synthesized and subsequently polymerized in order to form a pendant-like polymer. However, since the solubility of the phthalocyanine skeleton is low, in this method, it is necessary to introduce a soluble substituent such as a long-chain alkyl group or an alkoxy group into the aromatic ring of isoindoline included in the phthalocyanine skeleton in order to enhance reactivity. Furthermore, in order to bond the phthalocyanine structure to the polymer chain at one site, it is necessary to synthesize phthalocyanine that includes an amino group at one site, which serves as a reactive substituent, and to perform isolation purification using column chromatography or the like. Therefore, in this method, reaction yield is likely to be low and, when used as a mixture, a compound in which the phthalocyanine structure is bonded to a polymer chain at multiple sites may be produced as a byproduct.
In the method described in Laibing Wang et al, Polym. Chem. 2014,vol. 5,issue 8,pp. 2872-2879,The Royal Society of Chemistry, United Kingdom, for the same reason, it is also necessary to introduce a soluble substituent that is a long-chain alkoxy group into an isoindoline ring included in a phthalocyanine skeleton.
In the methods described in Japanese Patent Laid-Open Nos. 03-113462 and 06-148927,it is necessary to increase the amount of dispersant used in order to achieve a certain level of pigment dispersibility. Thus, there is a risk that the excessive amount of dispersant may affect the properties of the product depending on the application of the pigment.
The method described in Japanese Patent Laid-Open No. 2012-067285,in which a compound including an azo skeleton structure is used as a pigment dispersant, enables a compound capable of enhancing the dispersibility of various pigments to an acceptable level to be produced. However, a pigment dispersant having a higher capability of enhancing pigment dispersibility has been anticipated in order to meet a recent demand for an improvement of the quality of output images.